Catheters are used in various interventional procedures for delivering therapeutic means to a treated site (e.g., body organ or passageway such as blood vessels). In many cases, a catheter with a small distal inflatable balloon is guided to the treated site. Once the balloon is in place it is inflated by the operator for affixing it in place, for expanding a blocked vessel, for placing treatment means (e.g., stent) and/or for delivering surgical tools (e.g. knives, drills etc.) to a desired site. In addition, catheter systems have also been designed and used for retrieval of objects such as stents from body passageways.
A type of catheter developed for intravascular use is an over-the-wire (OVT) catheter. OVT catheter systems are characterized by the presence of a full-length guide wire, such that when the catheter is in its in situ working position, said guide wire passes through the entire length of a lumen formed in, or externally attached to, the catheter. OVT systems have several operational advantages which are related to the use of a full length guide wire, including good stiffness and pushability, features which are important when maneuvering balloon catheters along tortuous and/or partially occluded blood vessels. Despite a number of different OTW balloon catheter systems currently known in the art, there is a continuous need for a system that can more efficiently and safely collect plaque debris and other particulate matter from the lumen of internal body passages such as pathologically-involved blood vessels.
US published patent application No. 2007/0083158 incorporated herein by reference in its entirety, describes an OVT balloon catheter system having an intussuscepting balloon and including a pressure regulating mechanism for preventing pressure changes within the catheter and the balloon using an overpressure valve for releasing inflation fluid upon pressure increases over a pressure threshold or by using a syringe-like part formed in the catheter outer conduit to accommodate the fluid ejected from the balloon during intussuscepting of the balloon. The operator of the catheters described in US published patent application No. 2007/0083158 may monitor the degree of proximal pulling of the inner conduit of the catheter by monitoring a scale provided on the inner conduit of the catheter while pulling the inner conduit proximally to cause intussuscepting of the catheter's balloon. While this may enable the operator to assess the degree of movement of the inner conduit within the outer conduit, such monitoring may require time and attention of the operator which may unnecessary increase the time required for the procedure, and may also result in operator error in reading the scale. It would therefore be advantageous to enable the operator to perform all the necessary steps for operating the catheter without having to pay attention to any scale while still ensuring that the balloon is not accidentally damaged by excessive pulling of the inner conduit in the proximal direction.
In the catheters described in US published patent application No. 2007/0083158, if the length of the balloon or the crossing (inflated) diameter of the balloon changes, the entire syringe-like structure will need to be matched to the dimensions of the balloon in order to ensure that a sufficient amount of inflation fluid is accommodated by the syringe like structure during intussuscepting of the balloon. This fact may necessitate the production and stocking of a large number of different catheter parts for producing catheters with different balloon dimensions. This may be undesirable from a cost and logistical point of view and may involve increased cost of manufacturing, assembling and stocking of such catheters and/or catheter parts. Additionally, from the operational point of view, the necessary variations in the length and/or diameter of the syringe-like structure needed for different lengths and/or different diameters of balloons may result is substantial variations in the catheter system size and dimensions which may cause confusion and necessitate longer training of medical personnel.
Furthermore, the catheters described in US published patent application No. 2007/0083158, disclose the use of a safety lock for preventing axial movements of the inner conduit within the outer conduit. The safety lock comprises a u-shaped gripping clip for gripping the inner tube. A part of the safety lock 14 penetrates the wall of the outer conduit of the catheter through a tight orifice formed in the outer conduit of the catheter. Such an arrangement is relatively cumbersome to implement and test because it necessitates the use of sealing gaskets for rendering the orifice fluid tight and may leak inflation fluid and/or cause reduction of the pressure within the balloon during the inflation of the balloon. Furthermore, under certain circumstances, if the safety lock is in the locked position such that the u-shaped gripping clip is gripping the inner tube, the inner tube may still be moved distally within the outer conduit if a force accidentally applied the inner conduit by the operator overcomes the friction by the gripping clip and the inner conduit, which may result in ejection of captured debris from the intussuscepted balloon into the body passage or blood vessel.
US published patent application No. 2009/0204069 incorporated herein by reference in its entirety, discloses rapid exchange (RE) catheters having intussuscepting balloons with pressure regulating mechanisms similar to those used in the OVT catheters of published US patent application No. 2007/0083158.